Grinders or hammermills of the type widely used for grinding clay and shale in industries such as brick making generally include a housing and a rotary hammer assembly. The hammer assembly includes a plurality of rotatable discs or spiders between which the hammers are mounted by means of suspension pins. The hammers are mounted such that the clay or shale material is crushed between them as the hammer assemblies rotate.
As stated, the hammers are mounted for free swinging movement on the rotor discs or spiders by means of suspension pins which extend through aligned holes in either the disc or the spider and the hammer shank. The hammers are mounted between the discs at close tolerances just sufficient for clearance. There is approximately 1/8 inch tolerance between the side walls of the hammer shank or arm and the sidewalls of adjacent rotor discs.
Because of the constant swinging movement of spider or the hammers on the suspension pins, and because of the constant cloud or fog of abrasive dust created by the clay and shale, the adjacent side surfaces of the rotor discs and spiders are subject to extreme wear from the hammer shank, or the constant wear of metal against metal.
Various approaches to protecting the rotor disc from other types of wear are illustrated in a variety of patents. One approach which is of particular interest is shown in U.S. Pat. No. 4,222,530 to Whitney. That approach utilizes a replaceable cap of wear resistant metal on the end discs of a rotor shredder which do not have a swinging hammer shank adjacent thereto. The shredder disclosed therein is of a design utilizing a spider arm hammer assembly. It is important to note that the only rotor discs thereon are the end discs adjacent the housing walls. The side walls of the spiders, between which are carried the hammers, are left unprotected. Only the exposed edge of the spider arms are covered with a protective cover. The replaceable caps used on the end discs as disclosed by Whitney include a U-shaped channel which receives a curved portion of the periphery of the end disc therein. When the cap is in position on the disc, holes in the sidewalls of the cap are aligned with specially drilled holes in the end disc, and mounting pins are inserted therethrough and secured in place by welding a washer thereon. The cap is thus retained in place on the end disc by the welded pin and washer. When it is necessary to replace one of the caps, each of the welded pins must be broken and removed. The cap is then replaced and new pins welded into place. The procedure is thus expensive in that it is time consuming and requires considerable investment in parts, tools and labor.
Applicant's device was designed to improve the life of the end and interior discs and to overcome many disadvantages of the prior art devices. The present invention is particularly adapted for shredders of the type having a plurality of end and inside discs with hammers mounted therebetween.
At the outset the discs (inner and outer) are provided with a unique peripheral hole pattern in which there is a plurality of holes exceeding in number the number of hammers carried between each adjacent pair of discs. The holes are aligned and suspension pins or rods inserted through each aligned set of holes. Some, but not all, of the suspension rods have hammers mounted for free swinging movement thereon. Preferably the number of holes in each disc is a common multiple of the different numbers of hammers likely to be carried by various hammermills. For example, most hammermills carry either 3, 4, or 6 hammers between each set of discs. Therefore twelve (12) equally spaced holes are generally provided in the hole pattern, and if a hammermill has 3 hammers between each adjacent pair of discs, they may be located in four different positions, thus extending the life of the discs (or protective cap) four times; similarly a four hammermill can be positioned three times and a six hammermill twice before the discs (or protective caps) are completely worn and must be replaced.
Further in the present invention a replacement cap or protective shoe provided which is of a U-shaped configuration and is made of a wear-resistant metal, but the similarities to the Whitney device end there. The replaceable cap of the present invention is easily mounted or removed because the caps are held in place by the suspension rods alone. Therefore they may be easily removed and replaced when required, and a plurality of which may be secured in position by the same suspension rods on which the hammers are rotatably mounted.
The replaceable, wear resistant caps can also be repositioned along the periphery of the rotor discs. Each of the U-shaped caps include a cap portion and opposing sidewalls, and a plurality of apertures in each sidewall, which apertures are aligned with adjacent ones of the aforementioned apertures in the rotor disc. The cap is placed over an arcuate portion of the periphery of the rotor disc with the sidewall of the cap overlying a portion of each surface of the disc. A suspension rod is then inserted through each of the sets of apertures to hold the caps in place. The suspension rods are of a length sufficient to extend through all the discs and hammers in the rotor assembly. Thus, when the caps or hammers need to be repositioned or replaced it is a simple operation to unfasten and remove the suspension rods, automatically freeing the caps and the hammers for removal. Obviously each of the suspension rods does not have a hammer suspended therefrom. However, each of the apertures in the protective cap must have a suspension rod extending therethrough to prevent the cap from rocking and wobbling on the disc. If, as is described hereinabove the rotor discs have twelve apertures spaced around the periphery, and protective caps cover the outer periphery of the disc, then twelve suspension rods are required to secure the caps. However, there will generally be only three, four or six hammers mounted between each adjacent pair of discs.
Therefore, the present invention is a hammermill having an improved rotor disc and replaceable protective disc cap, with the parts having a significantly increased life and wear resistance. The disc caps protect the outer periphery of the rotor discs and significant portions of the disc sidewalls from wear caused by the freely swinging hammers. Relocation of the hammers extends the life of the caps, because normal wear can be spread over a wider area. Further, the caps utilized on the end or outer rotor discs include a flange depending outwardly from the cap portion of the channel perpendicular to the outer sidewall, which flange protects the ends of the suspension rods and also keeps clay and shale from falling down between the outer discs and the hammermill housing.
The objects of the present invention thus include the provision of an improved replaceable, protective cap for the end and intermediate rotor discs of a hammermill, the replaceable cap being designed to protect the side surfaces and the outer edge of the rotor discs.
It is also an object of the present invention to provide a rotor assembly for a hammermill which is designed such that the hammers can be repositioned at various arcuate positions between adjacent rotor discs to evenly distribute the wear on the discs or disc caps.
A still further object of the invention is the provision of means for quickly and easily replacing or repositioning the hammers and protective caps with a minimum amount of machine downtime.